The Supreme Court heard arguments Wednesday on whether people in states where the federal government runs the health insurance marketplaces are eligible for subsidies. The court's ruling is expected at the end of its term, in late June or possibly early July. If it decides against subsidies in the federal marketplaces, millions of Americans could be affected.

How many people could lose their subsidies?

If the court rules against the Obama administration in the King v. Burwell case, about 7.5 million people could lose their subsidies in 34 states that use the federal health care marketplace. The status of people in three other states — Oregon, Nevada and New Mexico — is unclear because those states at one time intended to run their own marketplaces but now rely on the federal government to manage them. Minnesota operates its own exchange.

How would insurance coverage change?

Prepare for falling dominoes. Within a matter of weeks, the HealthCare.gov system would have to stop providing tax credits to people in the affected states. Many of those people would find premiums unaffordable without the subsidies and would drop their coverage. Yet those who are sick and need insurance would probably try to hang onto their coverage, as healthy people dropped out. Insurers say this inevitably results in premiums spiraling upward.

What about the rest of the states?

States that run their own insurance marketplaces would be unaffected by a court ruling, meaning a widening gap between insurance coverage in the two groups of states.

What is corporate America's take on the case?

The hospital and health-insurance industries are backing the administration. Trade groups for those industries are also urging the court to back nationwide subsidies.

How will the states react?

Under any court ruling, states will have the power to restore their residents' subsidies if they establish their own exchanges. It would not be easy, but some states face more hurdles than others. Rep. Paul Ryan of Wisconsin, the chairman of the House Ways and Means Committee, has said his party will design a "bridge out of Obamacare" for people in the affected states. There's no agreement among Republicans on how such a policy would work.

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